Removable denture retaining structure

ABSTRACT

The specification discloses a removable denture retaining structure in which an elastic mounting member is provided between a denture body and an support base. 
     This structure can obviate all problems of the prior art, i.e. many parts are required, skilled technique is also required to produce, mount and dismount the denture body, and looseness and breakage due to fatigue are apt to occur. 
     Furthermore, the invention is advantageous because the structure can provide patients with comfortable feeling during use.

This is a division of application Ser. No. 652,314, filed Sept. 19, 1984now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to improvements in denture retainingstructures and more particularly to improvements in removable retainingstructures composed of support bases and denture bodies for removabledentures, removable crown and bridge (hereafter both are simply referredto as dentures).

2. Prior Art

Known retaining structures which retain such dentures on jaws so thatthey are removable when required for cleaning or repair are mainlymetallic retaining structures. One structure for example uses a screw oranother fixture to connect an support base with a denture body. Anotherstructure uses a metallic inner crown placed over a natural remainingtooth and capped by a metallic outer crown secured in a denture body toprovide a telescopic structure.

The former structure, however, uses many parts and requires skillsbecause mounting and removal are troublesome. The latter strucuture isapt to generate looseness and breakage due to wear caused by fatigue. Italso needs complicated and advanced technology.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to solve theseproblems. With this invention, an elastic mounting member made ofpolyurethane rubber, segment polyurethane rubber or composite materialsof these rubber materials is formed as desired and placed between asupport base and a denture. In the secured condition, a friction forcecaused by elastic compression and/or mechanical engagement of theelastic mounting member prevents the denture from sinking in or floatingfrom the support base during normal biting motion. When an externalforce different from the biting force is applied and the denture body isstrongly lifted, the member is elastically compressed and deformed, sothat the denture body can be removed upward from the support base. Sincethe member has good moldability, it can be molded in any forms anddimensions matching all tooth conditions. In addition, the member issuperior in elasticity, wear resistance and durability. As a result, theconstruction, fabrication and handling of the structure aresignificantly simplified. Preferred embodiments of this invention areshown in connection with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a longitudinal sectional view of the first embodiment of thepresent invention,

FIG. 2 is a longitudinal sectional view of the second embodiment of thepresent invention,

FIGS. 3 (A) to 3(I) are production process drawings of the secondembodiment of the present invention,

FIG. 4 is a longitudinal sectional view of the third embodiment of thepresent invention,

FIG. 5 is a longitudinal sectional view of the fourth embodiment of thepresent invention,

FIG. 6 is a longitudinal sectional view of the fifth embodiment of thepresent invention,

FIG. 7 is a top view of the sixth embodiment of the present invention,

FIG. 8 is an enlarged sectional view taken on the planes of the linesIIX--IIX of FIG. 7,

FIG. 9 is a longitudinal sectional view of the seventh embodiment of thepresent invention,

FIG. 10 is a longitudinal sectional view of the eighth embodiment of thepresent invention and

FIG. 11 is a longitudinal sectional view of the ninth embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A removable denture retaining structure which is commonly adapted forthe first to ninth embodiments of the present invention includes asupport base (1) and a denture body (2) which is removably secured onthe support base (1). The denture body (2) is integrated with an elasticmounting member (3) which is made of polyurethane rubber, segmentpolyurethane rubber or composite materials of these rubber materials andis formed as desired. The elastic mounting member (3) is mounted betweenthe support base (1) and the denture body (2) to prevent the denturebody from sinking in or floating from the support base (1) during normalbiting motion. When an external force different from the biting force isapplied and strongly lifted, the elastic mounting member (3) iselastically compressed and deformed so that the denture body can beremoved from the support base. The polyurethane rubber used in thepresent invention is made so that it has enough elasticity to provide asufficient friction force when compressed, to prevent the denture bodyfrom sinking in or floating from the support base during normal bitingmotion. The polyurethane rubber has also such elasticity characteristicsas to allow the denture body to be easily removed from the support basewhen an external force coping with the friction is applied to the rubberby a dentist. The polyurethane rubber has a module of elasticity of 10to 1,000 kg/cm², a coefficient of friction of 0.95 to 1.43 and acompression ratio of 0.46 to 0.50. The ranges of these physicalproperties can be further extended by copolymerization or composition asdescribed later. In addition, the polyurethane rubber is stable for anextended period when it is exposed to food, saliva and soldes. Therubber is not easily discolored (yellowed) so that it is nice to look atfor a long time. More specifically, polyether polyol, acrylic polyol,polybutadiene polyol or polycarbonate polyol is preferably selected as amain structure to reduce bonding (or hydrophile property due to bonding)of ester, aliphanate, buret, etc. which is apt to be hydrolyticallydissociated by weak acids (organic acids) or weak alkalis in a mouth. Inaddition, XDI (xylene diisocyanate), HDI (hexamethylene diisocyanate),HTDI (hydro TDI), HMDI (hydro MDI), IPDI (isophorone diisocyanate) orLDI (lysine diisocyanate) is preferably used as diisocyanate to reduceyellowing due to sunlight.

Two examples of polyurethane rubber materials with the abovementionedphysical and chemical properties are described below.

EXAMPLE 1

About 30 to 50 parts of IPDI are added to and reacted with 100 parts ofpolycarbonate polyol (molecular weight:2,000) at 100° C. for about 30minutes, and then mixed with 30 to 50 parts of 3,3'-dichloro,4,4'-diamino-diphenylmethane.

EXAMPLE 2

About 25 to 70 parts of HDI are added to and reacted with 100 parts ofpolybutadiene polyol (molecular weight:600), and then bridged by3,3'-dichloro, 4,4'-diamino-diphenylmethane.

These two are only examples.

The physical properties of the polyurethane rubber used for the presentinvention need to be changed according to the case in which the elasticmount member is used. In particular, the hardness, modulus of elasticityand coefficient of friction need to be changed. Chemically denaturedrubber, physically composite rubber or intermediate materials of theserubber materials can be used to meet the needs. To increase thehardness, acrylate, ester maleate, methacrylate, styrene, epoxy, fluorocompound or silicon carbide is included in the side or main chain ofpolyurethane rubber to produce a copolymer, i.e., segment polyurethanerubber. Modulus of elasticity and coefficient of friction can beincreased by physically blending polyurethane or the above-mentionedsegment polyurethane rubber with PVC, chlorinated polyethylene, AS, ABS,cellulose propionate, silicone oil, polyether sulfone, bisphenol A -epichlorohydrin resin or polytetramethylene-tetraphtalate, or bypartially chemically bonding the exemplified polymer with polyurethanerubber or segment polyurethane rubber to produce a polymer blend. Theproduct made by the former method is a physically composite material andthe product made by the latter method is an intermediate material ofchemical and physical composites. In the same way, polyurethane rubberor segment polyurethane rubber can also be composited with the followinginorganic and organic substances. That is, polyurethane rubber orsegment/polyurethane rubber can be compositied with organic fibers suchas polyester fiber, polyamide fiber and aramid fiber, or ceramic fiberssuch as glass fiber, alumina fiber and carbon fiber, or metal fibers.Furthermore, polyurethane rubber or segment polyurethane rubber can becomposited with powder of the organic fibers. Moreover, fabrics made ofthese fibers can be molded and integrated with the elastic mount member.

The physical properties of these chemical and physical compositedmaterials have the following wider ranges :

a modulus of elasticity of 10 to 10,000 kg/cm², a coefficient offriction of 0.03 to 1.8 and a compression ratio of 0.32 to 0.50. Theelastic mounting member of the present invention is made of theabove-mentioned polyurethane rubber, segment polyurethane rubber orcomposited materials of these rubber materials. However, low-foamedsubstances made of these rubber materials including a small amount offoam can also be used according to the case. The low-foamed substanceshave a better shock-absorbing function than solid substances.

If the foaming rate is too high, however, the desired elasticity may notbe obtained. Therefore, foamed substances with a very high foaming rateshould not be used.

In the case of another embodiment of the present invention, the elasticmounting member (3) is simply mechanically engaged with the support base(1) when the mounting member is mounted on the support base so that thedenture body can be prevented from floating from or sinking in thesupport base.

When the elastic mounting member (3) is lifted with a great force, it iselastically compressed and deformed so that the denture body can beeasily removed from the support base (1). In this case of the mechanicalengagement, the friction force caused by elastic compression is notregarded important. This embodiment differs from the previouslymentioned embodiment in this respect. However, to include bothembodiments in the present invention, the above-mentioned rubbermaterials need to be applied.

The embodiments of the present invention are classified as followsaccording to the performance of preventing denture body (2) fromfloating or sinking. The second embodiment corresponds to the formerembodiment species (which uses the friction force caused by elasticcompression), and the fourth and sixth embodiments correspond to thelatter embodiment species (which uses mechanical engagement). Otherembodiments (the first, third, fifth, seventh, eighth and ninthembodiments) correspond to both species. All embodiments will beconsidered in detail referring to the drawings. The first embodimentillustrates a denture of a lower jaw. As shown in FIG. 1, a naturalabutment tooth base (t) and a metallic post (12) function as the supportbase (1). The denture body (2) is shown as a denture plate which isplaced over the tooth (t). A metallic post (12) is embedded in the tooth(t), and a trapezoidal cap (35), which is placed over the post (12) andfunctions as the elastic mounting member (3), is integrated with thecrown (denture plate) (23) made of synthetic resins (such as acrylicresin or polyurethane resin). (ti) refers to an artificial tooth. Inthis embodiment, the elastic mounting member (3), i.e. the trapezoidalcap (35) is placed over the post (12) so that the denture body (2) isremovably connected with the tooth (t). More specifically, when anexternal force such as a biting force or a force to lift the tooth (ti)is applied to the connection (a lifting force is applied to the tooth(ti) when a sticky food such as rice cake is chewed and when the tooth(ti) separates from the mating natural tooth of an upper jaw), theconnection is firmly maintained in the vertical direction by thefriction force caused by elastic compression between the post (12) andthe elastic mounting member (3). In addition, such external force isbroken by the elastic deformation of the elastic mounting member (3).However, when a lifting force greater than the friction caused byelastic compression is applied to the tooth (ti) or the crown (23), thedenture plate (2) can easily be removed from the tooth base (t). Thesecond embodiment of FIG. 2 illustrates a removable crown. A metallicinner crown (11) and a natural tooth (t) function as the support base(1), and a metallic outer crown (21) functions as the denture body (2).A ring belt (31) inserted into the outer crown (21) functions as theelastic mounting member (3). (t) refers to a natural abutment tooth.When the outer crown (21) is placed over the inner crown (11), the ringbelt (31) is compressed around its entire circumference in its thicknessdirection. A restoration force is generated and applied to the innercrown as the friction force is caused by elastic compression.

This friction force prevents the outer crown (21) from sliding upwardeven when various external forces are applied to the outer crown (21).However, if an extraction force greater than the friction force causedby elastic compression is applied to the outer crown (21), the crown(21) can easily be removed. The thickness and shape of the ring belt(31) can be determined as desired. If the elastic mounting member (3)generates an excessive friction force, stripes (not shown) provided atappropriate intervals around the circumference can be used instead ofthe ring belt (31). The production process of the inner crown (11),outer crown (21) and ring belt (31) is explained referring to FIGS. 3(A)to 3(I).

First, a female model (5) with a cavity (50) which has the same shape asthe contour of a remaining natural tooth (not shown) is formed using animpression material as shown in FIG. 3(A). Next, the cavity (50) isfilled with plaster slurry to produce a reversed male model (6) as shownin FIG. 3(B). The male model (6) is placed upside down and a thin filmof wax is coated on the male model (6) to obtain a wax model (7) whichhas the same shape as the contour of the natural tooth. Then, the waxmodel (7) is invested in a mold (8) as shown in FIG. 3(D). The wax model(7) is heated and melted away to obtain a cavity (9) which has the sameshape as the contour of the wax model as shown in FIG. 3(E). Metal iscasted in the cavity (9) to produce an inner crown (11) as shown in FIG.3(F). By using this inner crown (11) as a model, a metallic outer crown(21) is made as shown in FIG. 3(G) in the same way as described above. Agroove (211) is formed on the inner circumference of the outer crown(21) by machining as shown in FIG. 3(H). Finally, polyurethane rubber orsegment polyurethane rubber is poured into the groove (211) and cured toproduce a ring belt (31) as shown in FIG. 3(I). As described in thissequential process, the elastic mounting member (3) can be made bysimply grooving the outer crown (21) and by pouring rubber in the grooveand curing it, although the inner and outer crowns (11) and (21) aremade using the conventional method. Since the ingredients ofpolyurethane rubber and segment polyurethane rubber have been adjustedto provide high flowability during low-temperature heating and at normaltemperatures, an ordinary machine can be used.

To obtain the elastic mounting member in which the above-mentionedfibers and powder are physically compounded with polyurethane rubber orsegment polyurethane rubber, the fibers and powder should be included inlost wax as required and prevented from flowing away when melted wax ismelted away so that they are integrated with cast polyurethane rubber orsegment polyurethane rubber. In the embodiments described later,polyurethane rubber or segment polyurethane rubber is also exemplifiedas a material of the elastic mounting member for convenience. Instead ofthe ring belt (31) of the second embodiment, the third embodiment uses anotch (33) projected from the inner surface of the outer crown (21) asshown in FIG. 4.

The tip end of the notch (33) is elastically fit into a recess (111) onthe outer side surface of the inner crown (11). It is obvious that thenotch (33) in this embodiment functions as a substitute for the ringbelt (3).

In the fourth embodiment, two natural abutment teeth (t), (t) and twobridge retainers (13), (13) function as the support base (1) and bridge(pontic) (22) functions as the denture body (2) as shown in FIG. 5. Twonotches similar to the notch of the third embodiment and are made ofpolyurethane rubber of segment polyurethane rubber, are integrated withthe bridge (22) and projected from the bridge. Each tip end of the notch(33) is mechanically engaged with the recess (111) on the outer sidesurface of each bridge retainer (13). In this embodiment, the bridge(22) is removable from the bridge retainers (13), (13). Elastic fittingof the notch (33) into the recess (111) applies unnecessary forces tonatural tooth (t), (t) and is not desirable.

The fifth embodiment is a modification of the fourth embodiment. Asshown in FIG. 6, two hat-shaped caps (34) provided in the bridge (22)function as the elastic mounting members (3). Each cap (34) is placedover a metallic post (112) projected from the outer surface of eachbridge retainer (13) to form a removable bridge denture. Due to the deepfitting between the cap (34) and the post (112), this structure can copewith greater external biting forces than the structure of the fourthembodiment. The sixth embodiment illustrates a bridge denture of a lowerjaw, which is a combination of a metallic rest (4) and the elasticmounting member (3) of the present invention. As shown in FIG. 8, whichis an enlarged sectional view taken on the planes of the lines IIX--IIXof FIG. 7, the rest (4) is stretched between two natural abutment teeth(t), (t) . The lower part of bridge (41) is provided under the rest (4),separated from the right and left the teeth (t), (t) via pockets (42),(42). Two elastic mounting members (3), (3) are included respectively inthe pockets (42), (42) and mechanically engaged with the support bases(1) and function as wedges (37). Since the elastic friction forces ofthe wedges (37), (37) are applied to the sides of the teeth (t), (t),this structure can sufficiently cope with forces which lift the bridge(22). The rest (4) receives the compression force applied to the bridge(22) during biting motion. Elastic fitting of the wedges (37) into thepockets is not desirable because of the same reason as described for thefourth embodiment. The seventh embodiment illustrates a bridge dentureover support bases composed of two kinds of implant members. As shown inFIG. 9, a natural abutment tooth (t), pin implant member (6) and bladeimplant member (7) function as the support bases (1), and the bridge(22) functions as the denture body (2). A hat-shaped caps (36), (36),(36), each made of polyurethane rubber or segment polyurethane rubber,are provided where the bridge (22) is placed over the support bases (t),(6) and (7). The bridge (22) is prevented from sinking in and floatingfrom the support base (t), (6) and (7) using a capping structuressimilar to that of the fifth embodiment. FIG. 10 illustrates the eighthembodiment. A cap (38) provided inside the metallic crown (21) functionsas the elastic mounting member (3). The cap (38) is made of low-foamedpolyurethane rubber or segment polyurethane rubber. The foamed materialfunction as a better shock absorber against external biting forces thana solid material.

FIG. 11 illustrates the ninth embodiment. A lower part of bridge (39),made of polyurethane rubber or segment polyurethane rubber, is locatedunder the metallic bridge (22), is integrated with the bridge (22) andfunctions as the elastic mounting member (3). This structure of thisembodiment provides better shock absorbing performance than thestructure of the previously mentioned embodiment in which the elasticmounting member (3) is used as a part of the bridge (22).

With this invention, as clearly understood from the above-mentioned nineembodiments, the elastic mounting member made of polyurethane rubber,segment polyurethane rubber or composite materials of these rubbermaterials and is placed between the support base and the denture.

In the secured condition, the friction force caused by compression ofthe elastic mounting member and/or mechanical engagement of the elasticmounting member prevents the denture body from sinking in or floatingfrom the support base during normal biting motion. This connection canbe released by applying a strong lifting force. Due to this simplestructure, the present invention is advantageous because it can solveall problems of the prior art, i.e. many parts are required, skilledtechnique is also required to produce, mount and dismount the denturebody, and looseness and breakage due to fatigue are apt to occur.Furthermore, unlike ready-made elastic members, the elastic mountingmember of the present invention can be molded in any shapes anddimensions according to the case. Therefore, this structure can providepatients with comfortable feeling during use.

Having described our invention as related to the embodiments shown inthe accompanying drawings, it is our intention that the invention be notlimited by any of the details of description, unless otherwisespecified, but rather be construed broadly within its spirit and scopeas set out in the accompanying claims.

We claim:
 1. A removable denture retaining structure including a supportbase and denture body, said removable denture retaining structure beingcharacterized in that said denture body is integrated with an elasticmounting member which is made from any of polyurethane rubber, segmentedpolyurethane rubber and composite materials of these rubber materialsand has at least the physical characteristics of the modulus ofelasticity of 10 to 10,000 kg/cm², a coefficient of friction of 0.03 to1.8 and a compression ratio of 0.32 to 0.50, and said elastic mountingmember is removably pressure-fitted to said support base to elasticallybe in frictional contact therewith, so that said denture body does notfloat from or sink in said support base during normal biting motion, andso that said denture body can be removed from said support base when agreat external force different from the biting force is applied toremove said denture body by compressing to deform said elastic mountingmember.
 2. A removable denture retaining structure as claimed in claim1, wherein said support base is a natural abutment tooth and an innercrown and said denture body is an outer crown.
 3. A removable dentureretaining structure as claimed in claim 2, wherein said elastic mountingmember is a ring belt buried inside said outer crown.
 4. A removabledenture retaining structure as claimed in claim 2, wherein said elasticmounting member is a cap provided inside said outer crown.
 5. Aremovable denture retaining structure as claimed in claim 4, whereinsaid cap is a low-foamed substance made of a material selected from thegroup consisting of polyurethane rubber, segment polyurethane rubber andcomposite materials of these rubber materials.
 6. A removable dentureretaining structure as claimed in claim 1, wherein said elastic mountingmember is two hat-shaped caps provided in said bridge, and each of saidcaps is placed over a post projected from the corresponding outersurface of said bridge retainer.
 7. A removable denture retainingstructure as claimed in claim 1, wherein said support base is a naturalabutment tooth and two implant members, said denture body is a bridge,and said elastic mounting member is two hat-shaped caps provided in saidbridge placed over said two implant members.
 8. A removable dentureretaining structure as claimed in claim 1, wherein said elastic mountingmember is a lower part of a bridge.